Ortofon MC A90 cartridge

Just a note regarding phono loading of the A90.

I initially had this set at 100 ohms but have now lowered to 47ohms. The difference can be startling - Al Di Meola's 'Alien chase on Arabian Desert' sounds awesomely huge and full of impact and atmospherics at 47ohms. Put the loading back to 100ohms and the sound becomes slightly bigger, but somewhat looser, less defined atmosphere and positioning/shape of instruments, less impact and excitement.

100 ohms can 'goose up' some recordings that lack air and atmosphere but mostly sounds less correct to me. YMMV.

Interestingly, Paul Seydor of TAS loads his Ortofon Windfeld (which uses essentially the same motor as the A90) at 40ohms.

System Details

Tobes, great pic of your A90! What camera/lenses did you use?

Jfrech,

The camera was just a Panasonic TZ7 (ZS3 in the US) point and shoot. I have no clues about photography...I take a bunch of shots and pick ones that look ok.

The pic on my webpage is a pretty low res reduction. The unreduced crop I posted in the pictures thread elsewhere shows more detail (but less context): Ortofon A90

This is essentially the classic ten times the internal impedance and it results in the flattest frequency response and thus the most neutral presentation. I also find no diminution of transient response or transparency. I agree that the raising the impedance to a hundred ohms--let alone running it unloaded--can produce some attractive artifacts, but artifacts they remain and most emphatically not accurate. They also become fatiguing after awhile.

Dear Tobes: I heard the A90 in my system loaded at 100 Ohms and I don't try it at 47 Ohms.

I can't say if at 47 Ohms or at 100 Ohms has the flatest frequency response, like Pseydor assume, because I don't measured it and I can't calculate either with out the cartridge inductance value.

What I can to know is that passing from 100 Ohms to 47 Ohms the SPL goes down almost 1db and this difference in SPL ( IMHO ) is the one that could makes that we hear " differences " other that a change in the frequency response due that the A90 internal resistance is so low ( 4 Ohms. ).

My thought is that the quality performance does not change but only the SPL. So to evaluate ( other than make the measurements in real time. ) what we are hearing we have to even the Phono stage/line stage output/volume at 47 Ohms and 100 Ohms.
We have to think that our ears/brain are extremely sensitive to tiny/small cganhes on SPL. Many times when we are hearing a recording with two different SPL: normally we like the one that has higher SPL.
In the other side, Pseydor say: " They also become fatiguing after awhile. ", this is correct because at 100 Ohms there is almost 1 db of higher SPL but not ( IMHO ) because is a quality differences other that the higher volume that can affect our perception " after awhile ".
Around 1 db on volume difference makes that the whole system performance change too.

Perhaps a little more important subject about is the input phono stage resistor quality where we are loading that cartridge.

Anyway, if that load impedance is the one value that works in your system that's fine because that value is the one that gives to you music enjoying.

Regards and enjoy the music,
Raul.